This invention relates generally to the providing or supplying of inflation gas and, more particularly, to the providing or supplying of such inflation gas via an elongated inflator such as may be desired for certain inflatable passive restraint systems for use in vehicles for restraining the movement of an occupant in the event of a vehicular collision.
It is well known to protect a vehicle occupant by means of safety restraint systems which self-actuate from an undeployed to a deployed state without the need for intervention by the operator, i.e., xe2x80x9cpassive restraint systems.xe2x80x9d Such systems commonly contain or include an inflatable vehicle occupant restraint element, such as in the form of a cushion or bag, commonly referred to as an xe2x80x9cairbag cushion,xe2x80x9d and a gas generator device, commonly referred to as an xe2x80x9cinflator.xe2x80x9d
In practice, upon actuation such as when the vehicle encounters a sudden deceleration, such as in the event of a collision, the inflator device serves to provide an inflation fluid, typically in the form of a gas, used to inflate an associated airbag cushion. Airbag cushions are typically used to deploy into one or more locations within the vehicle between the occupant and certain parts of the vehicle interior, such as the doors, steering wheel, instrument panel or the like, to prevent or avoid the occupant from forcibly striking such parts of the vehicle interior.
Various types or forms of such passive restraint assemblies have been developed or tailored to provide desired vehicle occupant protection such as based on either or both the position or placement of the occupant within the vehicle and the direction or nature of the vehicle collision, for example. In particular, driver side and passenger side inflatable restraint installations have found wide usage for providing protection to drivers and front seat passengers, respectively, in the event of head-on types of vehicular collisions. Driver side and passenger side inflatable restraint installations do not, however, generally provide as great as may be desired protection against vehicular impacts inflicted or imposed from directions other than head-on, i.e., xe2x80x9cside impacts.xe2x80x9d In view thereof, substantial efforts have been directed to developing inflatable restraint installations having particular effectiveness in the event of a side impact.
Upon deployment, the time period during which an airbag cushion remains pressurized is commonly referred to as xe2x80x9cstand-up time.xe2x80x9d In practice, driver side and passenger side airbag cushions are typically desirably designed to begin deflating almost instantaneously upon deployment such as to avoid presenting an undesirably hard or ungiving surface to an oppositely situated vehicle occupant. However, airbag cushions which provide substantially longer stand-up times may be required or desired in the event of certain accidents or collisions in order to provide a level of occupant protection suitable in the event of such an occurrence. For example, one particularly troublesome form of side impact is commonly referred to as a xe2x80x9croll-over.xe2x80x9d In a roll-over incident, a vehicle may undergo a partial, complete or multiple roll-over. As will be appreciated by those skilled in the art, roll-over accidents can be particularly demanding on inflatable restraint systems. In particular, an airbag cushion designed to provide occupant protection in the event of a vehicle roll-over may be required or desired to remain pressurized for an extended or prolonged period of time, as compared to usual or typical driver side and passenger side airbag installations. For example, a roll-over protection side impact airbag cushion may called on to desirably remain pressurized or provide a stand-up time such as extending for as long as about 5 seconds or more.
One particularly effective form of side impact inflatable restraint is the subject of Hxc3x85land et al., U.S. Pat. No. 5,788,270, issued Aug. 4, 1998, the disclosure of which patent is hereby incorporated by reference herein in its entirety and made a part hereof. Inflatable elements, such as disclosed in Hxc3x85land et al., U.S. Pat. No. 5,788,270, may desirably include an inflatable portion formed from two layers of fabric with the front layer and the back layer of the fabric woven together at selected points. In particular embodiments, such selected points are arranged in vertically extending columns and serve to divide the inflatable part into a plurality of vertical parallel chambers. The spaces between the selected points permit internal venting between adjacent chambers of the inflatable element. Particular such inflatable devices/elements, such as utilized in applications to provide protection over an extended area and having a generally planar form, are frequently referred to as xe2x80x9cinflatable curtains.xe2x80x9d
A one piece woven construction has been found to be a particularly effective method of forming such inflatable element airbag cushions. In particular, one piece woven constructions have been found to provide a relatively low cost method of constructing suitable such airbag cushions which provide desired stand-up times. While inflatable element airbag cushions can, as is known in the art, be fabricated of various materials, nylon 6,6 has been found to be a particularly effective and useful material for use in the making or manufacture of inflatable curtain elements such as described above and having a one piece woven design.
Many types or forms of inflator devices have been disclosed in the art for use in inflating inflatable restraint system airbag cushions. In at least certain particular inflatable passive restraint system installations, an inflator device having a flexible form or construction is desired. For example, in at least certain installations which involve inflatable curtain restraints, the use of an inflator device having a flexible form or construction can desirably serve to permit such an inflator device to more easily conform or fit within a selected storage volume in the vehicle, such as within the vehicle headliner along the roofline. As a result, incorporation and use of flexible inflator devices can provide or result in improved fit or installation within a vehicle.
One particularly common type or form of inflator device used in inflatable passive restraint systems is commonly referred to as a pyrotechnic inflator. In such inflator devices, gas used in the inflation of an associated inflatable element is typically derived from the combustion of a solid pyrotechnic gas generating material. While various combustible pyrotechnic materials are available, gas generant compositions commonly utilized in the inflation of automotive inflatable restraint airbag cushions have previously most typically employed or been based on sodium azide. The gas generated by the combustion of such pyrotechnic materials can be very hot and may contain variously sized particulate material. In practice, it is relatively common to include within such inflator devices one or more filters or the like elements effective to either or both remove such particulate and reduce the temperature of the gas prior to discharge therefrom. Nevertheless, gas discharge temperatures in the range of about 1300 K are common for conventional pyrotechnic inflator devices. In view thereof, it is common to include within an associated airbag cushion a heat resistant coating or one or more strategically placed patches of heat resistant material such as to minimize or avoid direct contact of the hot inflator discharge onto unprotected airbag cushion material. Further, in particular applications which rely on an inflation gas having a significantly elevated temperature, attaining desired stand-up times for or with the associated airbag cushion can prove difficult as the volume of the inflation gas reduces as the gas cools.
Further, while various flexible inflator devices containing or employing solid gas generant materials have been previously proposed, such solid-containing inflator devices have generally been subject to certain limitations or drawbacks, even in those inflator constructions which employ solid gas generant materials in a powdered form. In particular, solid-containing inflator devices are commonly subject to problems associated or related with: ignition and flame spread, difficulty in attaining and maintaining a desired distribution of the solid along the length of the inflator, as well as fretting or mechanical wear of the solid such as due to or resulting from flexing of the inflator device housing.
Another common form or type of inflator device utilizes or relies on a stored compressed gas. Upon actuation, such devices release the stored gas into an associated airbag cushion to effect the inflation thereof. While such inflator devices may reduce or avoid problems relating to particulate and hot gas discharges, such inflators generally require the potentially long-term storage of a material under pressure. Such long-term pressure storage can raise concerns regarding undesirable leakage over the course of the relatively long design lifetimes of such systems once installed in vehicles. As will be appreciated, providing for such storage under pressure can require application and use of substantial containment features for the material stored under pressure. In practice, such containment features are commonly evidenced by a relatively thick-walled, rigid containment chamber. Further, it is generally difficult to provide desired flexibility in an inflator design which employs such a thick-walled, rigid containment chamber.
Yet another common form or type of inflator device utilizes or relies on a combination of stored compressed gas and combustion of a gas generating material, e.g., a pyrotechnic, to produce or form an inflation gas for an associated airbag cushion. Such an inflator device is commonly referred to as an augmented gas or hybrid inflator. As with the above-identified pyrotechnic inflators, such inflator devices may result in a gas having an undesirably large or high particulate content. Also, while the discharge from such a hybrid inflator device is generally at a reduced temperature as compared to a corresponding pyrotechnic inflator, the temperature of such discharge may still be undesirably high for certain applications. Further, such inflator devices may suffer from at least some of the possible complications and related concerns regarding the potentially long term storage of a material under pressure. In addition, the provision of such inflator devices in a flexible form is generally subject to the same limitations or drawbacks discussed above relative to those inflator devices which contain solid gas generant or compressed gas, respectively.
In view of the above, there is a continuing need and demand for improved inflator devices, for inflating inflatable restraint elements, which overcome one or more of the above-identified problems. In particular, there is a need and a demand for an inflator device having a shapable form or construction such as to facilitate desired installation or placement thereof in particular locations within the interior of a vehicle, such as along the roof line of a vehicle such as above a vehicle door. In particular, there is a need and a demand for such an inflator device particularly suited for use in conjunction with specific types of inflatable restraint elements, such as inflatable curtain forms or types of inflatable elements.
A general object of the invention is to provide an improved inflator device for inflating an inflatable restraint device as well as an improved method of gas production.
A more specific objective of the invention is to overcome one or more of the problems described above.
The general object of the invention can be attained, at least in part and in accordance with one preferred embodiment of the invention, through an inflator device for inflating an inflatable restraint device and which inflator device includes an enclosed housing having an elongated length and opposed first and second ends. The inflator device also includes a quantity of a gas generant material disposed within the housing. The gas generant material is desirably in a non-gaseous, fluid form and substantially extends between the first and second ends of the housing. The inflator device further includes an initiator device disposed adjacent the housing. The initiator device, upon actuation, has a discharge portion in reaction initiating contact with at least a portion of the quantity of the gas generant material disposed within the housing and wherein upon actuation, the initiator device initiates reaction of the gas generant material to produce inflation gas.
The prior art generally fails to provide an elongated inflator of suitable design and construction such as to desirably permit the inflator device to be shaped to a non-linear elongated axis form and such as may be desired to facilitate installation or placement thereof in particular locations within the interior of a vehicle, such as along the roof line of a vehicle such as above a vehicle door. In particular, the prior art generally fails to provide such an inflator device particularly suited for use in conjunction with specific types of inflatable restraint elements, such as inflatable curtain forms or types of inflatable elements. That is, the prior art generally fails to provide such an inflator device having or being of sufficiently flexibility and small enough diameter to facilitate such placement in a vehicle while simultaneously providing sufficient inflation gas in sufficient quantities and at desired point(s) in time to provide desired side impact protection.
The invention further comprehends an inflator device for inflating an inflatable restraint device and which inflator device includes a tubular housing having an elongated length and opposed first and second ends. The inflator device also includes a quantity of a gas generant material disposed within the tubular housing. The gas generant material desirably has a non-gaseous, fluid form and substantially extends between the first and second ends of the tubular housing. The gas generant material contains a quantity of sensitizing gas selected from the group consisting of oxygen, nitrous oxide, carbon dioxide and mixtures thereof. The inflator device further includes an initiator device disposed adjacent the tubular housing and a sheath covering disposed about the exterior of the tubular housing. Upon actuation, the initiator device has a discharge portion in reaction initiating contact with at least a portion of the quantity of the gas generant material disposed within the tubular housing such that, upon actuation, the initiator device initiates reaction of the gas generant material to produce inflation gas resulting in opening of the tubular housing and release of at least a portion of the inflation gas therefrom. The sheath covering is effective to retain therewithin fragmentary portions of the tubular housing such as may be formed upon the opening thereof.
The invention still further comprehends an improvement in a method wherein a quantity of a liquid phase gas generant material is reacted to produce gas. In accordance with one embodiment of the invention, such improvement involves including a sufficient quantity of gaseous matter in the liquid phase gas generant material to improve reaction characteristics of the gas generant material.
As used herein, references to xe2x80x9ccombustion,xe2x80x9d xe2x80x9ccombustion reactionsxe2x80x9d and the like are to be understood to generally refer to the exothermic reaction of a fuel with an oxidant.
As used herein, references to xe2x80x9cdissociation,xe2x80x9d xe2x80x9cdissociation reactionsxe2x80x9d and the like are to be understood to refer to the dissociation, splitting, decomposition or fragmentation of a single molecular species into two or more entities.
xe2x80x9cThermal dissociationxe2x80x9d is a dissociation controlled primarily by temperature. It will be appreciated that while pressure may, in a complex manner, also influence a thermal dissociation such as perhaps by changing the threshold temperature required for the dissociation reaction to initiate or, for example, at a higher operating pressure change the energy which may be required for the dissociation reaction to be completed, such dissociation reactions remain primarily temperature controlled.
An xe2x80x9cexothermic thermal dissociationxe2x80x9d is a thermal dissociation which liberates heat.
xe2x80x9cEquivalence ratioxe2x80x9d (xcfx86) is an expression commonly used in reference to combustion and combustion-related processes. Equivalence ratio is defined as the ratio of the actual fuel to oxidant ratio (F/O)A divided by the stoichiometric fuel to oxidant ratio (F/O)S:
xcfx86=(F/O)A/(F/O)Sxe2x80x83xe2x80x83(1)
(A stoichiometric reaction is a unique reaction defined as one in which all the reactants are consumed and converted to products in their most stable form. For example, in the combustion of a hydrocarbon fuel with oxygen, a stoichiometric reaction is one in which the reactants are entirely consumed and converted to products entirely constituting carbon dioxide (CO2) and water vapor (H2O). Conversely, a reaction involving identical reactants is not stoichiometric if any carbon monoxide (CO) is present in the products because CO may react with O2 to form CO2, which is considered a more stable product than CO.)
For given temperature and pressure conditions, fuel and oxidant mixtures are flammable over only a specific range of equivalence ratios. Mixtures with an equivalence ratio of less than 0.25 are herein considered nonflammable, with the associated reaction being a decomposition reaction or, more specifically, a dissociative reaction, as opposed to a combustion reaction.